The invention relates to an electromagnetic linear drive and more particularly to a computerized electromagnetic linear drive which includes a computerized control center for controlling a stator which constitutes a path of movement for a vehicle and which is equipped with current conductors and divided into a plurality of motor elements. A movable vehicle which is equipped with magnets, preferably permanent magnets, cooperates with the stator to provide an electromagnetic linear drive. A plurality of energy supply units, each including a power control unit, is associated with each individual motor element and each is adapted to be switched on and off individually, preferably by sensors disposed along the path of movement which are influenced by the vehicle.
An electromagnetic linear drive wherein the vehicle itself effects self-control as regards the switch-on and switch-off of individual sections of the stator by means of sensors disposed along the path of movement which are influenced by the vehicle is known in the prior art. Known linear drive motor train systems are controllable, if desired, fully automatically, by a control center computer preferably coordinated with the entire path of movement of the vehicle. Individual running speed control signals must be applied to the individual sections of either the stator or the motor elements in order to obtain a desired running characteristic along the path of movement. On one hand, these signals must correspond to a basic running characteristic which includes stopping stations and line sections requiring slow-down, such as curves, as well as accelerating line sections, line sections for constant speed movement, and braking line sections. On the other hand, the basic running program must be variable as regards the level of the desired traveling speed so as to permit adaptation to varying demands.
By utilizing a circuit arrangement not only in the control center but also in each motor element a rather great expenditure of funds is involved to supply the individual motor elements with individual, variable running speed control information. As the number of motor elements is typically great and the path of movement long, this control is rather complicated and the costs are quite high. Besides, a great number of quick data lines are required to supply individual, varying speed control information to the individual motor elements. This is another factor contributing to the high expenditure and great costs involved in such a train system.
It is, therefore, an object of the invention to provide an improved electromagnetic linear drive of the type specified initially such that the running characteristic and running speed control can be effected at considerably less expenditure.
This object is met, in accordance with the invention, in that a memory device is associated with the power control unit of each motor element, in which memory different running speed control signals may be stored corresponding in number to the number of predetermined, selectable running programs. These running speed control signals are utilized to control the respective energy supply unit which supplies power to a motor element, resulting in a locally specific speed of the vehicle or train which runs over that motor element. The locally specific speed corresponds to the running program selected and lies in a range of from running speed zero to a locally specific maximum speed which is preset individually for each motor element. Advantageous further developments are recited in the claims.
A number of different running programs, each designated by a selected program number are fixed for the electromagnetic linear drive according to the present invention. These program numbers are stored in the memories of the individual motor elements. In each motor element each of these program numbers corresponds to a certain stored nominal speed. In different motor elements identical program numbers may be associated with different nominal speeds.
All that is needed with the present invention to produce a pattern of the running characteristic, i.e. a nominal speed as a function of the path of movement, is to report the desired program number to the individual motor elements. Each motor element then associates a particular nominal speed from the stored plurality of nominal speeds to the program number selected. The sum of these selected speeds of the individual motor elements provides the pattern of the overall running characteristic of the linear drive. If this running characteristic is observed, the arrangement found along the path of movement will produce the desired running conditions as to acceleration or speed. Of course, it should be obvious that a maximum speed which can be called up is limited to one of the program numbers. Any deviation from the selected pattern of the running characteristics can be eliminated by active control of the individual motor elements effecting a comparison between the nominal speed of the motor elements associated with a respective program number and the actual speed of the vehicle above this motor element measured by the sensors.
The term "vehicle" is used in the present context to designate not only an individual vehicle but also a train composed of a plurality of vehicles.
The running program control mentioned above affords particular advantage in cooperation with an electromagnetic linear drive which includes equal performance motor elements, (all motor elements are designed for the same maximum performance) such as described in co-pending U.S. Patent Application Ser. No. 647,706, entitled "An Electromagnetic Linear Drive", filed of even date herewith. The electromagnetic linear drive disclosed in this co-pending application has each of its motor elements designed for equal maximum performance. Motor elements of different lengths are provided and the length of each motor element is determined by the local need for maximum performance per unit length. The local need which exists at the place of a specific motor element is determined in accordance with a predetermined maximum speed characteristic along the path of movement. A linear drive which comprises such equal maximum performance motor elements can be controlled especially advantageously by the method described herein. The input of different running program numbers into the memories of individual motor elements permits the selection of different running characteristics with running speeds below the maximum speed. The type of running program control described, by the way, is very well suited also for a rotary motor having a stator divided into stator sections which are adapted to be switched on and off by the rotor by means of sensors provided at the stator sections as described in the prior art.
Electromagnetic linear drives of the type specified herein normally comprise motor elements which are much shorter than a typical vehicle or train. For this reason the vehicle or train is always located above a plurality of motor elements. In accelerating or braking line sections this means that the head and tail of the vehicle, for example, are controlled to different speeds by the respective motor elements underneath them. By cooperation of all motor elements located under the respective vehicle, a nominal speed point is developed along the vehicle. At this point the vehicle speed corresponds to the speed which is controlled by the underlying motor element. This nominal speed point of the vehicle, however, depends on the load, i.e. on the weight added to the vehicle. This may have a disadvantageous influence, for example, at stops if the nominal speed point of the vehicle is displaced along the braking line sections in response to the added weight. Thus it will become more difficult to stop the vehicle exactly at a desired point. In this respect a preferred embodiment of the invention, as described herein provides a remedy. With this embodiment the motor element performance is corrected in each motor element in accordance with the respective desired running program. The correction takes into consideration not only the distance which the vehicle portion located above the motor element at issue has from the nominal speed point of the vehicle but also whether the vehicle portion located above this motor element is in front of or behind the nominal speed point, as taken in the direction of movement. By way of this correction the vehicle portions lying in front of the nominal speed point are given a lower speed by the motor elements underneath than would correspond to the selected running program number of a respective motor element. The opposite happens with vehicle portions located behind the nominal speed point. The memory associated with each motor element helps to determine how many units of vehicle portion have passed the respective motor element and where each of the vehicle portions which happens to be passing the motor element is located with reference to the nominal speed point. This speed correction along the length of the vehicle provides a nominal speed control with regard to the nominal speed point of the vehicle which is independent of the added weight. Thus it is easy to have the vehicle always stop with its nominal speed point exactly at the desired place of the stop. Moreover, the control correction described above also permits a constant thrust to be adjusted for an entire train so that no longitudinal forces will occur in the train.
Preferably the sensors provided for self-control of the driving stator magnetic field by the vehicle are used to count the vehicle portions passing above a motor element. Further details may be seen in the applicant's own DE-OS No. 30 42 497, the disclosure of which is especially referred to in this respect.
If the correction value for vehicle portions lying in front of and behind the nominal speed point is determined by counting the vehicle portions passing a motor element, and if the correction is made in accordance with the respective counting value, a train length signal may be applied, as specified herein so as to effect a train length correction. The train length signals applied to the individual motor elements then may be used to evaluate the counting value drawn upon for correction in response to the respective train length. In this manner the speed of the individual train or vehicle portions always may be corrected with reference to the same nominal speed point, regardless of the train length, e.g., to the longitudinal center of the train or vehicle.
It is possible to connect a control center to the individual motor elements in such a manner that the control center has access to the memory of each individual motor element. This requires a great expenditure as to data lines. With a preferred embodiment of the present invention, therefore, the memories associated with at least a number of motor elements are interconnected by a single data bus. The necessity of a decoder in each element is avoided by coupling the same program number code to each memory connected to this common data bus.
For a longer path of movement the memories of the motor elements would have to be designed so as to accommodate a great number of running program numbers if a sufficiently great flexibility is desired with regard to the selectably running characteristics. In this respect a preferred further development of the invention as recited herein provides for a combination of the motor elements in several line sections. The memories of the motor elements of each line section are commonly connected to a data bus which is coordinated for a particular line section. The memories of the motor elements of each line section comprise a certain number of line section running program numbers. As different line sections may be controlled by different line section running program numbers, there is a great variety of different combinations of overall line running characteristics which are available utilizing a relatively small number of line section running program numbers.
With the present invention, there is no need to connect the control center with each individual line section by a separate data bus because it is provided in accordance with a preferred further development of the invention, that the individual line sections are associated with different subcenters preferably at the stopping stations. The individual subcenters may be connected to series with the control center by a single data bus. The data information transmitted by the a control center to the subcenters comprises not only the line section running program number but also a subcenter code in order that the control center may have direct access to the individual subcenters. If one subcenter feeds several line sections, the data information supplied by the control center preferably contains additional line section selection data. The control center transmits control information to the subcenters, and each respective subcenter may use its decoder to select the information destined for that particular subcenter. This information is converted into information which can be understood by the line sections, and the converted information is applied to all memories of the line section in question.
In this manner very few data lines and relatively small memories associated with each motor element are sufficient to permit a great variety of overall line running characteristics.
If the control center should fail, each subcenter can operate in autarchic fashion to select a running program number which was set previously for this instance so that the running operations still may be continued.
Especially advantageous is a linear drive which combines the running program control described above with the concept of the equal performance motor elements in accordance with the aforementioned U.S. Patent Application Ser. No. 647,706, filed of even date herewith and entitled "An Electromagnetic Linear Drive" and/or with a path of movement switchover in accordance with the co-pending U.S. Patent Application Ser. No. 647,708, filed of even date herewith and having the same title and/or the energy supply unit comprising monophase controllers in accordance with the co-pending U.S. Patent Application Ser. No. 647,707, entitled "An Energy Supply Unit For A MultiPhase Electromagnetic Linear Drive", filed of even date herewith.